How kauri can help us achieve our climate change goals

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Like all New Zealanders, I am in awe of these majestic giants, their staggering age of 1000 years or more and their straight trunks without branching for 15m or more.

Their tall canopies of massive branches form an impressive second story of trunks, supporting an elevated forest of habitat for abundant epiphytes, insects, geckos and birds.

Kauri belongs to the genus Agathis, which is part of a family of conifers found in Australia, Papua New Guinea, New Caledonia and the wider Southwest Pacific. Of these trees – all commonly known as kauri or kauri pine – our New Zealand species is the southernmost.

Kauri trees on the Kauri Loop Track in the Hakarimata Scenic Reserve in Huntly.

Kauri trees on the Kauri Loop Track in the Hakarimata Scenic Reserve in Huntly.

Prior to human settlement, it is believed that kauri forests could have covered up to 1.5 million hectares of New Zealand; for some perspective, the whole country is about 13.5 million hectares.

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Carbon dating of kauri wood preserved in the Northland and Waikato swamps suggests that these forests existed more than 40,000 years ago. These numbers are all quite staggering and reflect the reputation of the kauri as the rangatira of our forests.

Kauri had a big role to play in shaping the landscape and early history of Aotearoa in New Zealand. They are considered a taonga and their health as a sign of the general well-being of the ngahere (forest) and the people.

Young kauris in the Coromandel Peninsula.

MWILLIAMSNZ/123RF/Stuff

Young kauris in the Coromandel Peninsula.

The place of kauri in te ao Māori is filled with special – and wonderful – images. In terms of whakapapa, kauri is related to Tāne, god of forests. Tāne, along with his siblings, separated Heaven Father Ranginui and Earth Mother Papatūānuku to make room for light and life. In this new space is the domain of Tāne: the forest and its living creatures, of which kauri is the greatest leader.

Many great kauri have been given their own names and are revered as lords of the forest. Some iwi and hapu regard Tāne’s legs as giant kauris, which have inspired many works of art.

Likewise, the association between kauri and tohora (whales), which are said to have exchanged skins, gives kauri its unique scaly bark. Early Maori, struck by the towering stature of the kauri, recounted how the whale once wanted the huge tree to live in the ocean like a brother. Unable to convince him, they agreed to exchange the skins, which is why the bark of the kauri is fine and full of resin.

Kauri, in turn, forms an important part of my own research genealogy. My mentor was the late Tony Beveridge, father of indigenous forest management and research in Aotearoa. He introduced me to the wonderful science of trees, including kauri, in my first role as a young scientist establishing a trial planting of kauri in the Coromandel.

Close up of Agathis australis cone and leaves.

PATRIK STEDRAK / ISTOCK / GETTY IMA / Stuff

Close up of Agathis australis cone and leaves.

We and other scientists on his team at the Forest Research Institute were inspired by his passion for native forests covering all aspects of ecology and restoring our natural heritage.

Among other large, striking native species such as tōtara (my other favorite native tree) and pūriri, kauri is very popular with Maori, especially in the North.

The qualities of kauri wood – straight, evenly grained and strong – made it an ideal wood for carving and building waka taua (war canoe). Where naturally durable tōtara was not available, northern tribes felled and dug suitable kauri for their canoes, some of which reached 20 meters or more in length.

With these uses and those of the Pākeha settlers in mind, I think one of the most remarkable and valuable aspects of kauri is the abscission of the branches. From the sapling stage, the lower horizontal branches of the kauri naturally detach cleanly from the trunk, leaving no lasting damage to the bark and no knots in the lower trunk. As the trees mature and the bark begins to peel naturally, any signs of branch scarring disappears: leaving the beautiful, clean kauri wood finish we know so well.

Despite kauri’s remarkable status, it was inevitable that his maneuverability would be quickly noted and exploited by Pākeha. From the mid-1800s to the 1940s, forests were decimated by fires, over-harvesting, and bleeding gums (cutting tree trunks to stimulate resin production).

The kauri cut in the late 1700s and early 1800s were large, isolated saplings (rickers) that grew near the sea. Their trunks were highly valued as replacement masts and spars for sailing ships. The lightweight, straight-grain ‘cowrie’ quickly proved unrivaled on board ship and became indispensable to the British Navy. The story persists that Nelson’s flagship, HMS Victory, carried the New Zealand kauri aloft during the Battle of Trafalgar.

The fame of the kauri as a timber tree grew rapidly due to its massive volumes of attractive fine-grained wood. In November 1820, the first shipment of export timber, 98 kauri spars, left New Zealand on HMS Dromedary. For more than a century, the kauri will be the only indigenous species exploited on such a large scale.

Apart from felling kauri, gum digging and tapping live trees were also endemic practices. Diggers also caused other damage to forests and native lands through illegal burning and excessive bleeding (producers today would say the damage was akin to debarking). Eventually it became a lucrative industry as kauri gum became a major export product until 1940.

Kauri dieback was first discovered in the Waitākere Ranges in 2006. Many tracks in the area have been closed to protect the remaining trees.

LAWRENCE SMITH/STUFF/Stuff

Kauri dieback was first discovered in the Waitākere Ranges in 2006. Many tracks in the area have been closed to protect the remaining trees.

The largest kauri to survive this period of intensive deforestation is Tāne Mahuta, found at Waipoua on the west coast of the Northland region. Although trumped for the title of tallest native tree in Aotearoa by the kahikatea, anyone who has visited this lord of the forest knows that it lives up to its name at over 51m tall. And Tāne’s 4.5m trunk diameter will challenge even the most dedicated eco-friendly.

We can thank a series of dedicated conservationists for the area containing Tāne Mahuta and its big brother, Te Matua Ngahere. Kauri destruction became a public issue in the 1940s, and in 1952 9,000 hectares in Waipoua, containing perhaps the last substantial remnant of kauri forest in New Zealand, was designated as a forest sanctuary.

Today, the Waipoua Forest Trust works in partnership with tangata whenua and DOC to restore the kauri forest through the establishment of the Millennium Forest since 2000, a living example of the potential for expansion of the Waipoua Forest. To this end, the Trust has planted over 1.5 million native trees, including kauri.

It is nice to see that in this forest the kauri is once again truly able to play its role as a home and protector of other forest creatures, with bird species such as the kākāriki, kākā and kārearea able to call Waipoua at home.

Kauri dieback disease on the Maungaroa Ridge Track in the Waitākere Ranges Regional Park above Piha, West Auckland.

SIMON SMITH/STUFF/Stuff

Kauri dieback disease on the Maungaroa Ridge Track in the Waitākere Ranges Regional Park above Piha, West Auckland.

You have probably heard of the kauri dieback disease, which has led to a strong public awareness campaign. It is a serious threat: and currently without cure or treatment. The disease, caused by a fungus-like organism, can kill kauri trees of all ages and has an extremely high rate of infected kauri trees starving to death by damaging the tree’s nutrient and water-carrying tissues.

As our scientists strive to better understand kauri dieback, our own actions as individuals are absolutely essential to help stop the spread of this disease. Respecting the rāhui placed on infected areas and thoroughly cleaning your shoes at designated stations after walking in the bush are more important than you might think.

As we look to the future of our planet, it is important to recognize that kauri is an incredible boon for carbon sequestration. The mature kauri forest contains over 3000 tons of carbon dioxide equivalent per hectare, among the highest carbon stocks in the country. When planted on good sites and well managed, Kauri is one of our fastest growing native trees. On average, kauri plantations can sequester more than 16 tons of carbon dioxide per hectare per year during the first 50 years.

Although the kauri is often too big to be a garden tree, I hope it remains a recognizable icon for younger generations of New Zealanders. There are many planted kauri trees growing in established gardens and green spaces in urban areas, as well as in our working rural landscapes. The distinctive conical shape of these relatively young kauri trees will provide decades of enjoyment to Kiwis who have learned to recognize these distinctive trees.

Our native trees are intrinsically linked to who we are as New Zealanders: the pōhutukawa at Christmas, the kāponga (silver fern) as a symbol of national pride, the golden kōwhai and, of course, our mighty kauri. As lord of the forest, he holds a special place within our ngahere and, with careful stewardship, will continue to be one of the greatest legacies we can leave for future generations.

Dr David Bergin is the Rotorua-based scientific and technical advisor for Trees That Count. He has produced several publications on a range of native tree species, including kauri, tōtara and pōhutukawa.

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